Method and structure for packaging a high efficiency electro-optics device

ABSTRACT

A method and a structure for packaging an electro-optics device are disclosed. A transparent material is added between the die carrier and the electro-optics device, so that the light emitted from the backside of the electro-optics device can be extracted. Furthermore, a light reflective layer is formed on the die carrier, and a pattern of the light reflective layer is designed to prevent the light from being reflected to the active layer, the reflecting decreasing light-emitting efficiency again.

FIELD OF THE INVENTION

[0001] The present invention relates to a method and a structure of anelectro-optics device. More particularly, the present invention relatesto a structure for packaging an electro-optics device with highefficiency and the forming method thereof.

BACKGROUND OF THE INVENTION

[0002] There are many kinds of light-emitting diodes that are utilizednow. According to the packaging method, the light-emitting diodes areclassified as through-hold light-emitting diodes, surface-mountedlight-emitting diodes, and flip-chip light-emitting diodes.

[0003] Referring to FIG. 1, a conventional packaging structurecomprising a light-emitting cell fixed on a die carrier is shown. Thelight-emitting cell comprises an epitaxial structure 10 formed on aconventional substrate 20. The epitaxial structure 10 comprises ann-type semiconductor layer, an active layer, and a p-type semiconductorlayer. With the progress that the semiconductor process has been making,after the epitaxial structure 10 is completed, a transparent substratecan be utilized to replace the conventional substrate 20 for increasingthe light-emitting diode's output intensity. In this way, the lightemitted by the light-emitting diode is not absorbed by the opaqueconventional substrate. The light-emitting cell can emit light from itstop and bottom surfaces, thereby increasing its light-emittingefficiency.

[0004] As shown in FIG. 1, a die carrier 30, such as a lead frame, aprint circuit board, or a header, is connected to the substrate 20 toform a first electrode of the light-emitting cell. The silver paste,conductive paste, or bond of eutectic is utilized to fix the cell-fixingsurface 40 between the light-emitting cell and the die carrier 30. Then,a second electrode 50 of the light-emitting cell is connected to anotherend of the lead frame 35. Thereafter, when the power is supplied to thedie carrier 30 and the lead frame 35, the epitaxial structure 10 oflight-emitting cell can emit light.

[0005] Referring to FIG. 2, when the light-emitting cell's substrate 70is made of the electrically insulating material, the silver paste isutilized to fix the light-emitting cell on the cell-fixing surface 95 ofthe die carrier 100 as described above. Then, the first electrode 80 andthe second electrode 90 on the light-emitting cell are respectivelyconnected to the die carrier 100 and the lead frame 105. Thereafter,when the power is supplied to the die carrier 100 and the lead frame105, the light-emitting cell's epitaxial structure 60 can emit light.

[0006] However, because the conventional light-emitting cell is directlyfixed on the die carrier, the light generated by the epitaxial structureis absorbed by the cell-fixing surface between the cell and the diecarrier. Although the conventional substrate has been replaced by thetransparent substrate, most of the light emitted from the substrate isstill absorbed by the cell-fixing surface. Therefore, the light-emittingefficiency is decreased, so that the advantage of light emitted fromboth sides of the light-emitting cell cannot be fully presented.

SUMMARY OF THE INVENTION

[0007] According to the above background of the invention, thecell-fixing surface absorbs the light emitted from the LED cell,resulting in a disadvantage that the light-emitting efficiency isreduced after the LED cell is fixed on the die carrier. Hence, thisinvention provides a method and structure for packing a high efficiencyelectro-optics device.

[0008] It is therefore an objective of this invention to provide amethod and a structure for packaging an electro-optics device. Atransparent material is added between the die carrier and theelectro-optics device, so that the light emitting from theelectro-optics device is not directly absorbed by the cell-fixingsurface.

[0009] It is therefore another objective of this invention to provide amethod and a structure for packaging an electro-optics device. A lightreflective layer is formed on the die carrier, and a pattern of thelight reflective layer is designed to prevent the light from beingreflected again back to the active layer, wherein the light reflectiondecreasing light-emitting efficiency.

[0010] It is therefore another objective of this invention to provide amethod and a structure for packaging an electro-optics device. With theutilization of the present invention, the requirement of increasing theoutput power for the electro-optics device can be substantially achievedby increasing the optical path of the electro-optics device.

[0011] In accordance with all aspects of this invention, the inventionprovides a structure for a high efficiency electro-optics device,comprising: a die carrier; a light reflective layer located upon the diecarrier for changing the emitted light to a reflected light and alsomaking part of the emitted light unparallel to the direction of thereflected light; a transparent layer located on the light reflectivelayer; and an electro-optics cell fixing on the transparent layer,wherein a first electrode and a second electrode are electricallyconnected respectively to the die carrier and a lead frame.

[0012] In accordance with the aforementioned objects of this invention,this invention provides a method for forming a high efficiencyelectro-optics device, comprising: providing a die carrier; forming alight reflective layer upon a surface of the die carrier, wherein thelight reflective layer has a pattern for changing an emitting light to areflecting light and making part of the emitted light unparallel to thedirection of the reflected light; forming a transparent layer upon thelight reflective layer; fixing an electro-optics cell on the transparentlayer; and respectively electrically connecting a first electrode and asecond electrode of the electro-optics cell to the die carrier and alead frame.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing aspects and many of the attendant advantages ofthis invention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

[0014]FIG. 1 is a cross-sectional view, showing a conventional packagingstructure comprising a light-emitting cell fixed on a die carrier;

[0015]FIG. 2 is a cross-sectional view, showing a conventional packagingstructure comprising a light-emitting cell having an electricallyinsulating substrate fixed on a die carrier;

[0016]FIG. 3A is a cross-sectional view, showing the packaging structureof a light-emitting cell fixed on a die carrier of the presentinvention;

[0017]FIG. 3B is showing another embodiment according to FIG. 3A,wherein the light reflective layer is located in the transparentconductor layer;

[0018]FIG. 4A is a cross-sectional view showing the packaging structureof a light-emitting cell fixed on a die carrier of the presentinvention;

[0019]FIG. 4B is showing another embodiment according to FIG. 4A,wherein the light reflective layer is located in the transparentconductor layer;

[0020]FIG. 5A is a cross-sectional view, showing the packaging structurecomprising a light-emitting cell having the electrically insulatingsubstrate fixed on a die carrier of the present invention;

[0021]FIG. 5B is showing another embodiment according to FIG. 5A,wherein the light reflective layer is located in the transparentconductor layer;

[0022]FIG. 6A is a cross-sectional view, showing the packaging structurecomprising a light-emitting cell having the electrically insulatingsubstrate fixed on a die carrier of the present invention; and

[0023]FIG. 6B is showing another embodiment according to FIG. 6A,wherein the light reflective layer is located in the transparentconductor layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] In order to obtain the advantage of the light emitted from bothsides of the light-emitting cell, FIG. 3A shows the cross-sectional viewof the present invention. Since the light absorption of the conventionalcell-fixing surface decreases the light-emitting efficiency of thelight-emitting cell, the present invention uses the casting technique toprovide a sinking die carrier 130 and a light reflective layer 145having a hemispheric lift 132, located upon the die carrier 130. Thelight reflective layer 145 is made of the material with highreflectance.

[0025] Then, a transparent conductor layer 140, such as an indium tinoxide (ITO) layer, a cadmium tin oxide (CTO) layer, a zinc oxide (ZnO)layer, an indium zinc oxide (IZO) layer, or a nickel oxide (NiO) layer,is formed upon the sinking surface of the die carrier 130; and thetransparent substrate 120 of the light-emitting cell is then fixed onthe transparent conductor layer 140. Consequently, the manufacturing ofthe first electrode is completed, and the electrical connections amongthe transparent substrate 120, transparent conductor layer 140, and diecarrier 130 are also completed.

[0026] When the light-emitting cell is fixed upon the transparentconductor layer 140, a second electrode 150 is electrically connected toanother lead frame 135. Thus, the packaging structure of theelectro-optics device of the present invention is obtained.

[0027] Referring to FIG. 3B, it shows that the light reflective layer146 is located in the transparent conductor layer 140 according to thestructure of FIG. 3A.

[0028] According to these two embodiments described above, when thelight is generated by the epitaxial structure 110 and emitted from thetransparent substrate 120, it runs through the transparent conductorlayer 140 and reaches the light reflective layer 145 or the lightreflective layer 146. Owing to the high reflectance of the lightreflective layer 145 or the light reflective layer 146, most of thelight is reflected out of the structure, and is not absorbed. In thisway, the light-emitting efficiency of the light-emitting cell can beincreased significantly.

[0029] Moreover, in order to prevent the light reflective layer 145 or146 from reflecting the light generated by the epitaxial structure 110once again back to the active layer of the epitaxial structure 110, thereflecting causing the light in the active layer to be re-absorbed thusdecreasing light-emitting efficiency of the light-emitting diode, thepresent invention provides a design of the light reflective layers 145and 146 with the hemispheric lifts 132 and 133. When the light generatedby the epitaxial structure 110 reaches the hemispheric lift 132 or 133,the light is reflected to various directions. Consequently, the light isnot reflected back to the active layer of the light-emitting cell 110again or absorbed by the active layer, the reflecting and absorbingphenomena decreasing the light-emitting efficiency of the light-emittingcell.

[0030] The pattern of hemispheric lifts 132 or 133 is only stated as anexample for the present invention, and the present invention is notlimited thereto. As shown in FIGS. 4A and 4B, the light reflectivelayers 147 and 148 have a pattern of grating structure respectivelylocated upon the die carrier 130 and in the transparent conductor layer140 to achieve the same effect as described above. Therefore, thegrating structure also can prevent the reflected light going back to theactive layer of the epitaxial structure 110. The designs or functionshave the similar features of the present invention.

[0031] Referring to FIG. 5A, it shows the cross-sectional view of alight-emitting cell fixed on a die carrier of the present invention,which has a substrate made of electrically insulating material. The diecarrier 200 has the same structure as described above. First, thepresent invention provides a sinking die carrier 200 on which ahemispheric lift 202 is formed by the casting technique. The lightreflective layer 215 on the hemispheric lift 202 has high reflectance.

[0032] Then, a transparent layer 210 is formed upon the sinking surfaceof the die carrier 200, and the transparent substrate 170 of thelight-emitting cell is fixed on the transparent layer 210. When thelight-emitting cell is fixed upon the transparent layer 210, a firstelectrode 180 and second electrode 190 is electrically connected toanother lead frame 205 and the die carrier 200. The packaging structureof the present invention is therefore obtained. Thus, when the lightgenerated by the epitaxial structure 160 emits onto the hemisphericallift 202, the light is reflected into various directions and may not goback to the active layer of the epitaxial structure 160 again.

[0033] Referring to FIG. 5B, it is another embodiment of the presentinvention according to the structure of FIG. 5A, wherein the lightreflective layer 216 is located in the transparent layer 210.

[0034] According to the two embodiments described above, when the lightis generated by the epitaxial structure 160 and emitted from thetransparent substrate 170, it runs through the transparent layer 210 andreaches the light reflective layer 215 or 216. Owing to the highreflectance of the light reflective layer 215 or 216, most of the lightis reflected out of the structure. In this way, the light-emittingefficiency of the light-emitting cell can be increased.

[0035] Moreover, in order to prevent the reflected light from going backagain to the active layer of the epitaxial structure 110 and lightabsorption of the active layer, the reflecting and absorbing phenomenacausing the reduction of the efficiency of the LED, the presentinvention provides a design of the light reflective layer 215 or 216with a hemispheric lift 202 and 203. When the light reaches thehemispheric lifts 202 and 203, the light is reflected to variousdirections so as to prevent the light from going back to the activelayer of the light-emitting cell 160 and being absorbed by the activelayer.

[0036] The pattern of hemispheric lift 202 or 203 of the lightreflective layer 215 or 216 is merely stated as an embodiment for thepresent invention, and the invention is not limited thereto. As shown inFIGS. 6A and 6B, the light reflective layers 217 and 218 have a patternof grating structure located respectively upon the die carrier 200 andin the transparent layer 210. Therefore, the grating structure also canprevent the reflected light from going back to the active layer of theepitaxial structure 160. The similar designs or functions have the samefeatures of the present invention located within the scope of thepresent invention.

[0037] In fact, the substrate made of electrically insulating materialof the present invention also can be replaced by a conductive material,so that electrodes of the light-emitting cell are located on the sameside for the purpose of increasing the light-emitting efficiency.

[0038] Because the light-emitting cell of the present invention is anactive device, the present invention also can apply to all the activelight-emitting devices such as laser diodes, and passive photo detectingdevices such as photo detecting diodes. With the utilization of thepackaging structure of the present invention, the light receivingefficiency of the photo-receiving device can be increased significantly.Consequently, the electro-optics device of the present invention canfurther apply to all the through-hold electro-optics devices,surface-mounted electro-optics devices, and flip-chip electro-opticsdevices.

[0039] It is therefore an advantage of this invention to provide amethod and a structure for packaging a high efficiency electro-opticsdevice. A transparent material is added to a location between the diecarrier and the electro-optics device, so that the light generated bythe electro-optics device is not absorbed by cell fixing surface so asto sharply increase the light-emitting efficiency. When the presentinvention is used in the passive devices especially in the photodetecting devices, which have the structure and forming method describedabove, the devices' light receiving area can be increased and thedevices' efficiencies can be improved.

[0040] It is therefore another advantage of this invention to provide amethod and a structure for packaging a high efficiency electro-opticsdevice. A light reflective layer is coated on the die carrier, and apattern of the light reflective layer is designed to prevent the lightfrom being reflected to the active layer so as to overcome thedisadvantage of the poor light-emitting efficiency of the light-emittingdevice. When the present invention is used in the passive devicesespecially in the photo detecting devices, which have the structure andforming method described above, the light receiving efficiencies of thephoto detecting devices can be increased and the sensitivity and theprecision of the devices can be improved.

[0041] It is therefore still another advantage of this invention toprovide a method and a structure for packaging a high efficiencyelectro-optics device. With the utilization of the present invention,the purpose of increasing the output power of the electro-optics devicecan be substantially achieved by increasing the optical path andlight-sensing angle of the electro-optics device.

[0042] As is understood by a person skilled in the art, the foregoingpreferred embodiments of the present invention are illustrations of thepresent invention rather than limitations of the present invention. Itis intended to cover various modifications and similar arrangementscomprised within the spirit and scope of the appended claims, the scopeof which should be accorded the broadest interpretation so as toencompass all such modifications and similar structure.

What is claimed is:
 1. A structure of a high efficiency electro-opticsdevice, comprising: a die carrier; an electro-optics cell having a firstelectrode and a second electrode electrically connected respectively tosaid die carrier and a lead frame having an opposite polarity withrespect to said first electrode and said second electrode; a transparentlayer located between said die carrier and said electro-optics cell forfixing said electro-optics cell on a surface of said transparent layer;and a light reflective layer located optionally in said transparentlayer and between said transparent layer and said die carrier, whereinsaid light reflective layer has a pattern for changing an emitted light,which is generated by said electro-optics cell, to a reflected light andpreventing said reflected light from going back to an active layer ofsaid electro-optics cell.
 2. The structure according to claim 1, whereinsaid die carrier is a through-hold lead frame.
 3. The structureaccording to claim 1, wherein said die carrier is a print circuit board.4. The structure according to claim 1, wherein said die carrier is aheader.
 5. The structure according to claim 1, wherein saidelectro-optics cell comprises a conducting substrate and an epitaxialstructure, and said first electrode and said second electrode arelocated on said conducting substrate and a plurality of differentepitaxial layers of said epitaxial structure.
 6. The structure accordingto claim 1, wherein said transparent layer is selected from the groupconsisted of an indium tin oxide (ITO) layer, a cadmium tin oxide (CTO)layer, a zinc oxide (ZnO) layer, an indium zinc oxide (IZO) layer, and anickel oxide (NiO) layer.
 7. The structure according to claim 1, whereinsaid electro-optics cell comprises an insulating substrate and anepitaxial structure, and said first electrode and said second electrodeare located on a plurality of different epitaxial layers of saidepitaxial structure.
 8. The structure according to claim 1, wherein saidpattern comprises a plurality of hemispheric lifts.
 9. The structureaccording to claim 1, wherein said pattern of said light reflectivelayer comprises a plurality of hemispheric and sinking forms.
 10. Thestructure according to claim 1, wherein said pattern of said lightreflective layer comprises a plurality of grating structures.
 11. Amethod for forming a high efficiency electro-optics device, comprising:providing a die carrier; forming a light reflective layer upon a surfaceof said die carrier to change an emitted light to a reflected light,wherein said light reflective layer has a pattern for diverging saidemitted light; forming a transparent layer upon said light reflectivelayer; fixing an electro-optics cell on said transparent layer; andelectrically connecting a first electrode and a second electrode of saidelectro-optics cell respectively to the said die carrier and a leadframe having an opposite polarity with respect to said first electrodeand said second electrode.
 12. The method according to claim 11, whereinsaid die carrier is a through-hold lead frame.
 13. The method accordingto claim 11, wherein said die carrier is a print circuit board.
 14. Themethod according to claim 11, wherein said die carrier is a header. 15.The method according to claim 11, wherein said electro-optics cellcomprises a conducting substrate and an epitaxial structure, and saidfirst electrode and said second electrode are located respectively onsaid conducting substrate and said epitaxial structure.
 16. The methodaccording to claim 11, wherein said transparent layer is selected fromthe group consisting of an indium tin oxide (ITO) layer, a cadmium tinoxide (CTO) layer, a zinc oxide (ZnO) layer, an indium zinc oxide (IZO)layer, and a nickel oxide (NiO) layer.
 17. The method according to claim11, wherein said electro-optics cell comprises an insulating substrateand an epitaxial structure, and said first electrode and said secondelectrode are located on a plurality of different epitaxial layers ofsaid epitaxial structure.
 18. The method according to claim 11, whereinsaid pattern comprises a plurality of hemispheric lifts.
 19. The methodaccording to claim 11, wherein said pattern of said light reflectivelayer comprises a plurality of hemispheric and sinking forms.
 20. Themethod according to claim 11, wherein said pattern comprises a pluralityof grating structures.
 21. A method for forming a high efficiencyelectro-optics device, comprising: providing a die carrier; forming afirst transparent layer upon a surface of said die carrier; forming alight reflective layer upon said first transparent layer to change anemitted light to a reflected light, wherein said light reflective layerhas a pattern for diverging said emitted light; forming a secondtransparent layer upon said light reflective layer; fixing anelectro-optics cell on said second transparent layer; and electricallyconnecting a first electrode and a second electrode of saidelectro-optics cell respectively to the said die carrier and a leadframe having an opposite polarity with respect to said first electrodeand said second electrode.
 22. The method according to claim 21, whereinsaid die carrier is a through-hold lead frame.
 23. The method accordingto claim 21, wherein said die carrier is a print circuit board.
 24. Themethod according to claim 21, wherein said die carrier is a header. 25.The method according to claim 21, wherein said electro-optics cellcomprises a conducting substrate and an epitaxial structure, and saidfirst electrode and said second electrode are located on said conductingsubstrate and a plurality of different epitaxial layers of saidepitaxial structure.
 26. The method according to claim 21, wherein saidfirst transparent layer and said second transparent layer are selectedfrom a group consisting of an indium tin oxide (ITO) layer, a cadmiumtin oxide (CTO) layer, a zinc oxide (ZnO) layer, an indium zinc oxide(IZO) layer, and a nickel oxide (NiO) layer.
 27. The method according toclaim 21, wherein said electro-optics cell comprises an insulatingsubstrate and an epitaxial structure, and said first electrode and saidsecond electrode are located on a plurality of different epitaxiallayers of said epitaxial structure.
 28. The method according to claim21, wherein said pattern comprises a plurality of hemispheric lifts. 29.The method according to claim 21, wherein said pattern of said lightreflective layer comprises a plurality of hemispheric and sinking forms.30. The method according to claim 21, wherein said pattern comprises aplurality of grating structures.